• Christoph Lameter's avatar
    [PATCH] Remove policy contextualization from mbind · 5fcbb230
    Christoph Lameter authored
    Policy contextualization is only useful for task based policies and not for
    vma based policies.  It may be useful to define allowed nodes that are not
    accessible from this thread because other threads may have access to these
    nodes.  Without this patch strange memory policy situations may cause an
    application to fail with out of memory.
    
    Example:
    
    Let's say we have two threads A and B that share the same address space and
    a huge array computational array X.
    
    Thread A is restricted by its cpuset to nodes 0 and 1 and thread B is
    restricted by its cpuset to nodes 2 and 3.
    
    Thread A now wants to restrict allocations to the first node and thus
    applies a BIND policy on X to node 0 and 2.  The cpuset limits this to node
    0.  Thus pages for X must be allocated on node 0 now.
    
    Thread B now touches a page that has never been used in X and faults in a
    page.  According to the BIND policy of the vma for X the page must be
    allocated on page 0.  However, the cpuset of B does not allow allocation on
    0 and 1.  Now the application fails in alloc_pages with out of memory.
    Signed-off-by: default avatarChristoph Lameter <clameter@sgi.com>
    Cc: Andi Kleen <ak@muc.de>
    Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
    5fcbb230
mempolicy.c 30 KB